ABU DHABI // Scientists are rethinking theories about the resilience of coral reefs in the Arabian Gulf following a new study.
Corals worldwide tend to thrive at temperatures of about 28°C but struggle and die when temperatures reach three or four degrees higher, an occurrence known as coral bleaching.
But in the Gulf, corals can tolerate temperatures as high as 34°C, with bleaching not occurring until temperatures of 35 to 36°C – a fact that has long bewildered scientists.
The resilience of Gulf corals may now be better understood thanks to a research project by teams from New York University Abu Dhabi (NYUAD) and the National Oceanography Centre (Nocs) at the University of Southampton.
The project, which started in 2011, took coral samples from the waters around Abu Dhabi to the United Kingdom so that the algae living in the coral tissue could be studied and classified.
"Corals have a symbiotic relationship with algae that live within their tissue and provide them with food," explained Dr John Burt, head of the marine biology laboratory at NYUAD.
"There are many groups of such algae out there and some are considered more tolerant of high temperatures than others."
The scientists' hypothesis was that within the Gulf corals, algal species highly tolerant to heat stress would dominate.
However, the results of the project, published this week in the scientific journal Marine Pollution Bulletin, show otherwise.
The scientists found that the prevalent algal species were the same as those found in other climates – known as "generalist" types – despite these species not usually being found in corals exposed to high temperatures.
"We see that the algae are indeed special in Gulf corals but in a way that we did not expect," said Dr Joerg Wiedenmann, head of the coral reef laboratory at Nocs.
"Our results suggest that the algae are not solely responsible for the heat resistance of Gulf corals and that we need to look closer into other mechanisms that might render the corals more resilient."
Dr Burt said that the results may offer hope that corals were more resilient to heat stress than previously thought.
"Clearly, corals in the Gulf are capable of pulling off some tricks that science hasn't yet figured out," he said.
The scientists are continuing their collaboration with further samples of corals from the Arabian Gulf and the Gulf of Oman.